Aromatic polycarbonate resin composition and moldings

ABSTRACT

Provided is an aromatic polycarbonate resin composition which comprises 100 parts by mass of an aromatic polycarbonate resin and from 0.001 to 1 part by mass of an additional thermoplastic resin that differs from the aromatic polycarbonate resin in the refractive index by at least 0.001 and which is so designed that the ratio (X)/(Y) is at least 0.5 wherein (X) indicates the spectral transmittance at 320 nm through a sample plate of the resin composition having a thickness of 2 mm and (Y) indicates the spectral transmittance at 633 nm through it. Having realized further increase in the transparency of aromatic polycarbonate resin, the resin composition gives moldings of which the transparency is comparable to that of acrylic resin for optical use, and the resin moldings have good impact resistance and heat resistance.

TECHNICAL FIELD

[0001] The present invention relates to an aromatic polycarbonate resincomposition and moldings. Precisely, it relates to an aromaticpolycarbonate resin composition and moldings of good transparency, whichare favorable, for example, for optical devices such as optical lensesand optical waveguides, as well as for display panels and illuminatorcovers, and for substitutes for glass.

BACKGROUND ART

[0002] As having the advantages of impact resistance, heat resistance,good electric properties and transparency, aromatic polycarbonate resinsare used in various fields. In particular, because of their excellenttransparency, they are favorably used for various applications ofoptical devices such as optical lenses and optical waveguides, and alsofor optical information-recording media, display panels, illuminatorcovers, and other substitutes for glass. In some applications thereof,however, the transparency of aromatic polycarbonate resins is oftenunsatisfactory.

[0003] For example, backlight units for liquid-crystal image displaysand those for various guide lights generally have a built-in surfacelight source of a transparent tabular molding that emits lightuniformly. The transparent tabular molding receives the light from amain light source, cathode ray tube (fluorescent lamp) combined with it,and emits light from its surface, and this is referred to as an opticalwaveguide. The material for such an optical waveguide must not attenuatelight that passes through it, and is preferably lightweight and wellworkable.

[0004] From these viewpoints, it has heretofore been said thatpolymethyl methacrylate (PMMA) of thermoplastic resins is the mostsuitable for optical devices. The overall parallel light transmittancethrough PMMA is on a high level, falling between 91 and 93%, and thetransparency of PMMA is extremely high. In view of its good transparencyand workability, therefore, PMMA is an extremely excellent resin foroptical devices. However, the heat resistance, the impact resistance andthe flame retardancy of PMMA are not always satisfactory. Therefore, theproblem with PMMA is that its service conditions are limited for opticalwaveguides, display panels and illuminator covers.

[0005] For example, optical waveguides for backlights for instrumentpanels, tail lamps and winkers for automobiles must satisfy therequirements of thermal deformation resistance at 120° C. or higher andfalling weight impact strength of at least 10 J, and for these, PMMA isoften impracticable.

[0006] In their practical use, aromatic polycarbonate resins have noproblem in point of the heat resistance and the impact resistancethereof, but their transparent is far inferior to that of PMMA.Therefore, for optical applications such as optical waveguides, etc., itis desired to increase the level of the transparency of aromaticpolycarbonate resins.

[0007] Various compositions prepared by blending an aromaticpolycarbonate resin and an acrylic resin of higher transparency havebeen proposed. In general, a resin composition that comprisespolycarbonate and polymethyl methacrylate could not be a uniformtransparent resin, and it has heretofore been developed as a specificopaque resin having a pearly gloss. After that, some transparent resinshave become developed, taking the advantages of the two resins.

[0008] For example, <1> JP-B 56-28937 discloses a composition of apolycarbonate and a low-molecular acrylic copolymer that comprises from75 to 90% by mass of methyl methacrylate and from 10 to 25% by mass ofalkyl acrylate. However, in order that the composition could betransparent, the molecular weight of the acrylic copolymer in thecomposition must be at most 15000, and the acrylic copolymer serves as aplasticizer in the composition. The problem with the compositiondisclosed is that the physical properties of the polycarbonate resin inthe composition are significantly worsened. Though not having anynegative influence thereon, the acrylic copolymer in the compositiondoes not improve the transmittance of the composition.

[0009] <2> JP-A 63-90551, 63-256647 and 64-1749 say that a copolymer ofmethyl methacrylate, mono-substituted (meth)acrylamide, maleinimide and(meth)acrylate having a carbon cyclic group is miscible withpolycarbonate to give a transparent composition. However, thecomposition is transparent only when it forms films, but is nottransparent when it forms moldings having a thickness of a few mm.Therefore, the composition is not applicable to optical materials andoptical waveguides.

[0010] To solve the problem, <3> JP-A 4-359953 and 4-359954 disclose animproved composition of an aromatic polycarbonate and a methacrylatecopolymer, in which the methacrylate copolymer has at least 50% by massof phenyl methacrylate units. However, as is obvious from Examples andComparative Examples given in these, the haze (%), one index oftransparency, of 2-mm sheets of the composition that contains 3% by massof methacrylate copolymer is from 5 to 8%, while, on the other hand, thehaze (%) of the same sheets of polycarbonate alone is 4%. This meansthat the transparency of polycarbonate resin is rather lowered whenmethacrylate copolymer is added thereto.

[0011] As in these, essential improvement of transparency ofpolycarbonate resin is in fact difficult even if polycarbonate resinwhich is transparent by itself is combined with acrylic resin havinghigher transparency.

[0012] <4> JP-A10-73725and 10-158364disclose a polycarbonate resincomposition of good light transmittance, which comprises 100 parts bymass of polycarbonate resin and from 0.001 to 1 part by mass of acrylicresin and in which the molecular weight of the acrylic resin preferablyfalls between 200 and 100,000. The composition disclosed differs fromthe other conventional compositions in point of the technical idea inthat the amount of the acrylic resin to be added to polycarbonate resinis at most 1 part by mass, and, in addition, the photoconductivity ofthe composition is good. Concretely, even when 0.2 parts by mass ofacrylic resin is added to 100 parts by mass of polycarbonate resin, thephotoconductivity of the resulting composition is comparable to that ofacrylic resin alone. In addition, the other advantages of thecomposition are that the composition has high impact resistance and goodheat resistance intrinsic to polycarbonate resin.

[0013] However, in the field of optical devices, further improvement ofthe transparency of polycarbonate resin is much more desired. Thecomposition <4> almost satisfies the transparency and thephotoconductivity of acrylic resin of an ordinary grade and iscomparable to such an ordinary-grade acrylic resin, but is stillinferior to high-transparency acrylic resin for optical use.

[0014] Given the current situation as above, the present invention is tofurther improve the transparency of aromatic polycarbonate resins, andits object is to provide an aromatic polycarbonate resin compositionthat gives moldings comparable to those of acrylic resins for opticaluse in point of the transparency not losing the characteristics of goodimpact resistance and heat resistance intrinsic to aromaticpolycarbonate resins, and to provide the moldings of the resincomposition.

DISCLOSURE OF THE INVENTION

[0015] We, the present inventors have assiduously studied therelationship between the transparency and the spectral transmittance ofaromatic polycarbonate resins. As a result, we have found that, when asmall amount of any other specific thermoplastic resin is added to anaromatic polycarbonate resin and when the dispersive condition of theresulting resin composition is specifically controlled, then thespectral transmittance of the aromatic polycarbonate resin composition,or that is, the light absorption pattern thereof varies, and thissignificantly contributes toward the improvement of the transparency ofthe resin composition. On the basis of these findings, we have completedthe present invention.

[0016] Specifically, the invention provides the following:

[0017] (1) An aromatic polycarbonate resin composition which comprises100 parts by mass of an aromatic polycarbonate resin and from 0.001 to 1part by mass of an additional thermoplastic resin that differs from thearomatic polycarbonate resin in the refractive index by at least 0.001and which is so designed that the ratio (X)/(Y) is at least 0.5 wherein(X) indicates the spectral transmittance at 320 nm through a sampleplate of the resin composition having a thickness of 2 mm and (Y)indicates the spectral transmittance at 633 nm through it.

[0018] (2) The aromatic polycarbonate resin composition of (1), whereinthe additional thermoplastic resin is an acrylic resin.

[0019] (3) The aromatic polycarbonate resin composition of (1) or (2),which contains from 0.005 to 0.2 parts by mass of a phosphorus-basedantioxidant relative to 100 parts by mass of the aromatic polycarbonateresin.

[0020] (4) The aromatic polycarbonate resin composition of (3), whereinthe phosphorus-based antioxidant is a pentaerythritol compound.

[0021] (5) The aromatic polycarbonate resin composition of (4), whereinthe phosphorus-based antioxidant isbis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol phosphite.

[0022] (6) The aromatic polycarbonate resin composition of any of (1) to(5), which contains from 0.01 to 2 parts by mass of a functionalgroup-containing silicone compound and/or an alicyclic epoxy compoundrelative to 100 parts by mass of the aromatic polycarbonate resin.

[0023] (7) A transparent molding of the aromatic polycarbonate resincomposition of any of (1) to (6).

[0024] (8) An optical waveguide made of the aromatic polycarbonate resincomposition of any of (1) to (6).

BEST MODES OF CARRYING OUT THE INVENTION

[0025] The invention is described in detail hereinunder.

[0026] The invention provides an aromatic polycarbonate resincomposition which comprises 100 parts by mass of an aromaticpolycarbonate resin and from 0.001 to 1 part by mass of an additionalthermoplastic resin that differs from the aromatic polycarbonate resinin the refractive index by at least 0.001 and which is so designed thatthe ratio (X)/(Y) is at least 0.5 wherein (X) indicates the spectraltransmittance at 320 nm through a sample plate of the resin compositionhaving a thickness of 2 mm and (Y) indicates the spectral transmittanceat 633 nm through it.

[0027] It is known that the optical properties such as the overallparallel light transmittance, the haze and the spectral transmittance ofaromatic polycarbonate resin significantly depend on the thickness ofthe test plate of the resin. It is also known that the spectraltransmittance of the resin greatly varies at a wavelength fallingbetween 290 nm and 400 nm (when the thickness of the test plate of theresin falls between 0.1 and 5 mm). The optical properties of thearomatic polycarbonate resin result from the molecular structure of theresin, and it has heretofore been considered impossible to improve theoptical properties of the resin.

[0028] Contrary to this, our studies have revealed that aromaticpolycarbonate resin compositions having improved spectral transmittancecharacteristics can be obtained. This our finding is novel. The improvedaromatic polycarbonate resin composition is obtained, for example, byadding, to an aromatic polycarbonate resin, a small amount of anadditional thermoplastic resin that differs from the aromaticpolycarbonate resin in the refractive index and by controlling thecondition for dispersing the two resins.

[0029] The principal ingredient of the aromatic polycarbonate resincomposition of the invention is an aromatic polycarbonate resin, andthis maybe any and everyone not specifically defined. For example, theresin may be produced through reaction of a diphenol and a carbonateprecursor. Concretely, a diphenol and a carbonate precursor may bereacted in solution or in melt; more concretely, a diphenol may bereacted with phosgene, or a diphenol may be reacted with a diphenylcarbonate through transesterification.

[0030] Various diphenols may be used, including, for example,2,2-bis(4-hydroxyphenyl)propane [bisphenol A],bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane,2,2-bis(4-hydoxy-3,5-dimethylphenyl)propane, 4,4′-dihydroxydiphenyl,bis(4-hydroxyhenyl)cycloalkane, bis(4-hydroxyphenyl) oxide,bis(4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone, bis(4-hydroxyphenyl) sulfoxide, bis (4-hydroxyphenyl) ether, and bis(4-hydroxyphenyl) ketone.

[0031] Especially preferred diphenols are bis(hydroxyphenyl)alkanes,especially those starting from bisphenol A. The carbonate precursorincludes carbonyl halides, carbonyl esters and haloformates, concretely,for example, phosgene, diphenol dihaloformates, diphenyl carbonate,dimethyl carbonate, and diethyl carbonate.

[0032] The aromatic polycarbonate resin may have a branched structure,for which the branching agent may be any of1,1,1-tris(4-hydroxyphenyl)ethane,α,α′,α″-tris(4-hydroxyphenyl)-1,3,5-triisopropylbenzene, phloroglucine,trimellitic acid, and isatin-bis(o-cresol). For controlling themolecular weight of the resin, usable is any of phenol, p-t-butylphenol,p-t-octylphenol, p-cumylphenol, and p-dodecylphenol.

[0033] The viscosity-average molecular weight of the aromaticpolycarbonate resin for use in the invention generally falls between10,000 and 100,000, but preferably between 11,000 and 40,000, morepreferably between 12,000 and 30,000. The viscosity-average molecularweight (Mv) of the resin is obtained as follows: The viscosity of theresin in methylene chloride at 20° C. is measured with an Ubbelohde'sviscometer, from which is derived the intrinsic viscosity [η] thereof.The viscosity-average molecular weight (Mv) of the resin is calculatedaccording to the following formula:

[η]=1.23×10⁻⁵ Mv^(0.83)

[0034] The aromatic polycarbonate resin composition of the invention hasthe spectral transmittance characteristic mentioned above. The aromaticpolycarbonate resin composition that has the spectral transmittancecharacteristic as above is obtained concretely by mixing 100 parts bymass of an aromatic polycarbonate resin and from 0.001 to 1 part by massof an additional thermoplastic resin that differs from the aromaticpolycarbonate resin in the refractive index by at least 0.001 (therefractive index of bisphenol A polycarbonate resin is 1.590), for whichthe dispersive condition the additional thermoplastic resin in thecomposition is specifically controlled. In order that the resultingaromatic polycarbonate resin composition may satisfy the spectraltransmittance characteristic as above, it is a matter of importance thatthe small amount of the additional thermoplastic resin added to theresin composition is finely dispersed in the moldings of the resincomposition.

[0035] The additional thermoplastic that differs from the aromaticpolycarbonate resin in the diffractive index by at least 0.001,preferably by 0.01 to 0.2 is not specifically defined, but is preferablyan acrylic resin. The acrylic resin is a resin that comprises repetitivemonomer units of, for example, from acrylic acid, acrylates,acrylonitrile and their derivatives, and it may be either a homopolymeror a copolymer with styrene, butadiene or the like.

[0036] Concretely, it includes, for example, polyacrylic acid,polymethyl methacrylate (PMMA), polyacrylonitrile, polyethyl acrylate,polyacrylic acid-2-chloroethyl copolymer, acrylicacid-n-butyl-acrylonitrile copolymer, acrylonitrile-styrene copolymer,acrylonitrile-butadiene copolymer, and acrylonitrile-butadiene-styrenecopolymer. Of those, especially preferred is polymethyl methacrylate(PMMA). In addition, the molecular weight of the acrylic resinpreferably falls between 200 and 100,000, more preferably between 10,000and 60,000 or so.

[0037] The aromatic polycarbonate resin composition of the inventioncomprises, for example, 100 parts by mass of such an aromaticpolycarbonate resin, and from 0.001 to 1 part by mass, preferably from0.05 to 0.5 parts by mass, more preferably from 0.1 to 0.3 parts by massof such an acrylic resin.

[0038] The aromatic polycarbonate resin composition of the invention maybe obtained, for example, by melting, kneading and shaping a shapingmaterial that comprises 100 parts by mass of an aromatic polycarbonateresin (e.g., bisphenol A polycarbonate resin) and from 0.001 to 1 partby mass of an acrylic resin such as polymethyl methacrylate (PMMA).

[0039] The shaping material to be shaped in melt is not specificallydefined, and, for example, it may be a dry blend of pellets, powders orflakes of aromatic polycarbonate resin and acrylic resin; or a dry blendof a master batch from a melt blend of aromatic polycarbonate resin andacrylic resin of relatively high concentration, with an additionalaromatic polycarbonate resin added thereto. If desired, aromaticpolycarbonate resin and acrylic resin may be blended in solution thatcontains a solvent of methylene chloride or ethylene chloride. In thiscase, acrylic resin of high concentration may be blended with aromaticpolycarbonate in solution to prepare a master batch of aromaticpolycarbonate resin with acrylic resin well dispersed therein, and theresulting master batch may be kneaded in melt with additional aromaticpolycarbonate resin and then pelletized to give ordinary resin pelletsfor shaping material.

[0040] Though the reason is not as yet completely clarified, thearomatic polycarbonate resin composition of the invention may realizethe intended specific spectral transmittance characteristic when acrylicresin is dispersed in the resin composition (or moldings) in a specificcondition, concretely, when the acrylic resin particles dispersed in theresin composition (or moldings) are so controlled that they are notmicroscopically definitely separated from each other.

[0041] For example, for the melt-kneading condition to give the resincomposition, acrylic resin must be fully dispersed in melt in aromaticpolycarbonate resin in the resulting resin composition, for which,therefore, the two resins must be kneaded at a relatively high shearforce. The melt viscosity of aromatic polycarbonate resin is relativelyhigh, and when the resin is kneaded in melt with acrylic resin, theshear condition for enhancing the dispersibility of the acrylic resin inthe resin composition will often cause thermal deterioration anddiscoloration of aromatic polycarbonate resin and even reduction in thespectral transmittance of the resulting resin composition. Therefore,taking these negative influences on the resin composition intoconsideration, it is a matter of great importance to suitably selectgood melt kneaders and good melt conditions favorable for the resincomposition of the invention.

[0042] Not detracting from the specific spectral transmittancecharacteristic thereof, the aromatic polycarbonate resin composition ofthe invention may contain various additives. For antioxidant to thecomposition, for example, preferred are phosphorus-based antioxidantssuch as phosphites and phosphates. The phosphites may be tri-, di andmonophosphites, including, for example, triphenyl phosphite,trisnonylphenyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite,trinonyl phosphite, tridecyl phosphite, trioctyl phosphite, trioctadecylphosphite, distearylpentaerythritol diphosphite, tricyclohexylphosphite, monobutyldiphenyl phosphite, monooctyldiphenyl phosphite,distearylpentaerythritol diphosphite,bis(2,4-di-tert-butylphenyl)pentaerythritol phosphite,bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol phosphite,2,2-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite, andtetrakis(2,4-di-tert-butylphenyl)-4,4-diphenylene phosphonite.

[0043] The phosphates include, for example, trimethyl phosphate,triethyl phosphate, tributyl phosphate, trioctyl phosphate, triphenylphosphate, tricresyl phosphate, tris(nonylphenyl) phosphate, and2-ethylphenyldiphenyl phosphate. One or more of these phosphorus-basedantioxidants may be in the resin composition either singly or ascombined.

[0044] Of those phosphorus-based antioxidants, especially preferred aredistearylpentaerythritol diphosphite,bis(2,4-di-ter-butylphenyl)pentaerythritol phosphite,bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol phosphite,tris(2,4-di-tert-butylphenyl) phosphite. More preferred arepentaerythritol phosphites; and even more preferred isbis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol phosphite.

[0045] The phosphorus-based antioxidant content of the resin compositionmay fall between 0.005 and 0.2 parts by mass, preferably between 0.01and 0.1 parts by mass, per 100 parts by mass of the aromaticpolycarbonate resin in the composition. In addition, the aromaticpolycarbonate resin for use in the invention may contain a functionalgroup-containing silicone compound and an alicyclic epoxy compound. Thefunctional group-containing silicone compound may be a functionalgroup-having (poly)organosiloxane, and its skeleton is a polymer or acopolymer having a basic structure of a formula:

R¹ _(a)R² _(b)SiO_((4−a−b)/2)

[0046] wherein R¹ represents a functional group-containing group; R²represents a hydrocarbon group having from 1 to 12 carbon atoms; and aand b satisfy the following: 0<a≦3, 0≦b<3, 0<a+b≦3. The functional groupincludes, for example, an alkoxy group, an aryloxy group, apolyoxyalkylene group, a hydrogen atom, a hydroxyl group, a carboxylgroup, a cyanol group, an amino group, a mercapto group, and an epoxygroup.

[0047] Regarding the functional group therein, the silicone compoundhaving multiple functional groups, or silicone compounds each having adifferent functional group may be combined for use herein. In thefunctional group-having silicone compound as above, the ratio offunctional group (R¹)/hydrocarbon group (R²) generally falls between 0.1and 3, preferably between 0.3 and 2 or so.

[0048] The silicone compound may be liquid or powdery, but is preferablywell dispersible in the resin composition while the composition iskneaded in melt. For example, one preferred example of the siliconecompound is liquid at room temperature, having a kinematic viscosity atroom temperature of from 10 to 500,000 mm²/sec. Even though the siliconecompound is liquid, it can be uniformly dispersed in the moldings of theresin composition, and it rarely bleeds out of the surfaces of themoldings while and after the moldings are formed. This is onecharacteristic advantage of the invention.

[0049] The amount of the functional group-containing silicone compoundthat may be added to the aromatic polycarbonate resin falls between 0.01and 2.0 parts by mass, but preferably between 0.05 and 1.0 part by mass,per 100 parts by mass of the resin. If its amount is smaller than 0.01parts by mass, the silicone compound will be ineffective for improvingthe thermal stability and the optical properties of the resincomposition; but if larger than 2.0 parts by mass, it may worsen theoptical properties of the resin composition.

[0050] The alicyclic epoxy compound is a cycloaliphatic compound havingan alicyclic epoxy group, or that is, having an epoxy group with oneoxygen atom added to the ethylene bond in the alicyclic ring.Concretely, the alicyclic epoxy compound includes, for example,1,2-epoxycyclohexane, 1,4-epoxyccylohexane,1-methyl-1,2-epoxycyclohexane, 1,3-dimethyl-1,2-epoxycyclohexane,1-methoxy-1,2-epoxycyclohexane, 1,4-epoxy-2-cyclohexane, and compoundsof the following formulae (1) to (5), wherein R represents H or CH₃ anda+b=1 or 2:

[0051] The amount of the alicyclic epoxy compound that may be in theresin composition may fall between 0.01 and 1.0 part by mass, butpreferably between 0.02 and 0.5 parts by mass per 100 parts by mass ofthe aromatic polycarbonate resin in the composition. If it is smallerthan 0.01 parts by mass, it will be ineffective for hydrolysisresistance and will also be ineffective for improving the opticalproperties of the resin composition; but if larger than 1. 0 part bymass, it will worsen the optical properties of the resin composition.

[0052] In addition to the components mentioned hereinabove, the aromaticpolycarbonate resin composition of the invention may further contain anyother various additives not specifically detracting from the effect ofthe invention if necessary. For example, the resin composition maycontain any of hindered phenols or amines for antioxidants;benzotriazoles or benzophenones for UV absorbents; hindered amines forlight stabilizers; aliphatic carboxylates, paraffins, silicone oils orpolyethylene waxes for internal lubricants, antistatic agents,colorants, mold releasing agents, flame retardants, etc.

[0053] One example of producing the aromatic polycarbonate resincomposition and its moldings is described below. The aromaticpolycarbonate resin composition of the invention may be produced, forexample, by dry blending a molding material of aromatic polycarbonateresin and PMMA in a ribbon blender, a drum tumbler, a Henschel mixer orthe like, followed by pelletizing the resulting blend through asingle-screw extruder, a double-screw extruder, a multi-screw extruderor the like into ordinary resin pellets. Thus formed, the resin pelletsare molded into various moldings. Regarding the condition formelt-kneading the blend in pelletizing it, the cylinder temperaturesuitably falls between 230 and 280° C. If the temperature is lower than230° C., it is unfavorable since the acrylic resin could not welldisperse in the pellets owing to melt failure and since the resin willyellow owing to high shear stress; but if higher than 280° C., it isalso unfavorable since the resin will also yellow at such hightemperatures. For good dispersion of acrylic resin in the resincomposition, the shear force to be applied to the constituent componentsbeing blended must be at least on a certain level or higher, and thecompression ratio, the screw design, the screw diameter and the screwrevolution of the extruder used for pelletization, and also the moldingtemperature at which the resin pellets are molded must be suitablydetermined.

[0054] Next, the pellets are generally molded into moldings in a modeof, for example, injection molding or extrusion molding, especiallypreferably through injection molding. In the process of injectionmolding to give the intended resin moldings, the cylinder temperature isgenerally set to fall between 260 and 320° C. The temperature issuitably determined, depending on the thickness and the size of themoldings to be produced, or that is, depending on the melt flow lengthof the resin composition being molded. Preferably, the mold temperaturefalls between 50 and 120° C. If it is lower than 50° C., the moldtransferability will be poor; but if higher than 120° C., the resinphase separation of aromatic polycarbonate resin/PMMA will be seriousand the transparency of the resulting resin moldings will lower. Anyhow,higher or lower temperatures than the defined range are unfavorable.

[0055] The transparent moldings of the invention are not specificallydefined, and they may be suitably designed in accordance with theirfinal applications. For example, they may be shaped in any desiredmanner, including, for example, flat plates, curved plates, notches,cups, boxes, etc. The aromatic polycarbonate resin composition and itsmoldings of the invention are so designed that the ratio (X)/(Y) is atleast 0.5, preferably at least 0.55, wherein (X) indicates the spectraltransmittance at 320 nm through a sample plate of the resin compositionhaving a thickness of 2 mm and (Y) indicates the spectral transmittanceat 633 nm through it. For forming the sample plate of the resincomposition having a thickness of 2 mm, the resin composition may beinjection-molded into the intended sample plate in the manner as above.The molding temperature may be selected from the range of from 260 to320° C. in accordance with the molecular weight of the aromaticpolycarbonate resin in the resin composition, and the mold temperaturemay fall between 60 and 110° C. or so.

[0056] The aromatic polycarbonate resin composition of the inventionrealizes increased light transmittance, not lowering the impactresistance and the heat resistance intrinsic to the aromaticpolycarbonate resin in the composition.

[0057] The aromatic polycarbonate resin composition of the inventionsignificantly differs from any other conventional aromatic polycarbonateresin compositions in point of the spectral transmittance, and it has acomplete light transmittance comparable to that of PMMA. Accordingly,the aromatic polycarbonate resin composition of the invention is usable,for example, for optical devices such as optical lenses and opticalwaveguides, and for various illuminator covers and display panels assubstitutes for glass.

[0058] The invention is described more concretely with reference to thefollowing Examples and Comparative Examples, which, however, are notintended to restrict the scope of the invention.

EXAMPLES 1 TO 3, AND COMPARATIVE EXAMPLES 1 AND 2

[0059] As in Table 1, the components were formulated (parts by mass) inthe ratio indicated, then kneaded in melt and pelletized through a screwextruder. The resulting pellets were dried at 120° C. for 12 hours, andthen injection-molded into sample plates (140 mm×140 mm×2 mm thickness)for spectral transmittance determination, sample plates (70 mm×70 mm×3mm thickness) for complete light transmittance determination, and othertest pieces for determination of physical properties. The molding resintemperature was 300° C.; and the mold temperature was 100° C. Thusformed, the sample plates and the test pieces were tested for theoptical properties, the heat resistance and the impact resistance. Thetest data obtained are given in Table 1.

[0060] The molding materials used herein, the condition forpelletization, and the methods for evaluating the samples are mentionedbelow.

[0061] 1. Molding Materials:

[0062] (A) Aromatic Polycarbonate Resin:

[0063] Toughlon FN1700A (by Idemitsu Petrochemical—this is a bisphenol Apolycarbonate resin having a viscosity-average molecular weight of18,000 and a refractive index of 1.590.

[0064] (B) Polymethyl Methacrylate (PMMA):

[0065] Dianal BR87 (by Mitsubishi Rayon), having a molecular weight of25,000 and a refractive index of 1.490.

[0066] Its molecular weight was measured as follows: Using an Ostwaldviscometer, the intrinsic viscosity [η] of the polymer in chloroform at25° C. was measured, and the mean degree of polymerization PA of thepolymer was derived from the thus-measured intrinsic viscosity [η]according to the following equation:

log PA=1.613 log ([η]×10⁴/8.29)

[0067] (C) Phosphorus-Based Antioxidant:

[0068] Irgafos 168 (by Ciba Speciality Chemicals)—this is tris(2,4-di-t-butylphenyl) phosphite.

[0069] Adekastab PEP-36 (by Asahi Denka)—this isbis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol phosphite.

[0070] (D) Functional Group-Containing Silicone Compound:

[0071] KR219 (by Shin-etsu Chemical Industry)—this is vinyl andmethoxy-having methylphenylsilicone having a kinematic viscosity of 18mm²/sec.

[0072] (E) Alicyclic Epoxy Compound:

[0073] Celoxide 2021P (by Daicel Chemical Industry)—this is the compoundof formula (1) mentioned above.

[0074] 2. Condition for Pelletization:

[0075] Condition [I]:

[0076] 70 mmφ single-screw extruder (L/D=36, compression ratio=1.6) isused. The cylinder temperature is 250° C.; and the screw revolution is100 rpm.

[0077] Condition [II]:

[0078] 40 mmφ single-screw extruder (L/D=28, compression ratio=2.7) isused. The cylinder temperature is 280° C.; and the screw revolution is100 rpm.

[0079] 3. Methods for Evaluation of Samples:

[0080] (1) Determination of Spectral Transmittance:

[0081] Device used: Shimadzu's UV-2400PC

[0082] Thickness of sample plate: 2 mm

[0083] (2) Determination of Complete Light Transmittance:

[0084] Using a test device of JIS K7105, the complete lighttransmittance of the sample plate was measured as follows:

[0085] The injection-molded sample plate (70 mm×70 mm×3 mm thickness) tobe tested was sandwiched between two injection-molded plates (70 mm×70mm×3 mm thickness) of Idemitsu Petrochemical's Toughlon HR2500(high-reflection material), and its complete light transmittance wasmeasured in that condition. The sample set was sealed with thehigh-reflection material plate so as to protect it from the lightleakage through the side exposed to light, to such a degree that thecomplete light transmittance through a control set of two plates ofToughlon HR2500 with no sample plate therebetween (with a cavity betweenthe two) could be 100%. The. aperture for the incident light was 10 mm×1mm.

[0086] (3) Thermal Deformation Temperature:

[0087] Measured according to the method A (1.81 MPa) of JIS K7207.

[0088] (4) Falling Weight Impact Strength:

[0089] Measured according to ASTM D3763-86.

[0090] The weight falling rate is 7 m/sec; and the load to the sample is36.85 N. TABLE 1 Example 1 Example 2 Example 3 Comp. Ex. 1 Comp. Ex. 2Aromatic Polycarbonate 100 100 100 100 100 PMMA 0.1 0.1 0.2 0 0.1Irgafos 168 0.02 0 0 0.02 0 PEP-36 0 0.05 0.05 0 0.05 KP219 0.1 0.1 0.10 0.1 Celoxide 2021P 0.05 0.05 0.05 0 0.05 Condition for Pelletization(I) (I) (I) (II) (II) Spectral Transmittance (%)   (X) 320 nm 52.6 57.559.3 34.7 43.2   (Y) 633 nm 90.8 91.0 91.2 89.0 90.0   Ratio of (X)/(Y)0.58 0.63 0.65 0.39 0.48 Complete Light Transmittance (%) 93.8 94.0 94.170.0 92.8 Thermal Deformation Temperature 130 130 130 130 130 (° C.)Falling Weight Impact Strength (J) 40 41 40 42 40

[0091] Industrial Applicability

[0092] Of the moldings of the aromatic polycarbonate resin compositionof the invention, the physical properties are not lowered as comparedwith those of the moldings of aromatic polycarbonate resin alone, andthe light transmittance is increased. Concretely, the transparency ofthe moldings is comparable to the optical grade of PMMA resin, onetypical example of high-transparency resins. Accordingly, the resinmoldings of the invention are expected to have more increasedapplications in the field of optical products in which PMMA resin couldnot be used because of its low heat resistance and impact resistance.

1. An aromatic polycarbonate resin composition which comprises 100 partsby mass of an aromatic polycarbonate resin and from 0.001 to 1 part bymass of an additional thermoplastic resin that differs from the aromaticpolycarbonate resin in the refractive index by at least 0.001 and whichis so designed that the ratio (X)/(Y) is at least 0.5 wherein (X)indicates the spectral transmittance at 320 nm through a sample plate ofthe resin composition having a thickness of 2 mm and (Y) indicates thespectral transmittance at 633 nm through it.
 2. The aromaticpolycarbonate resin composition as claimed in claim 1, wherein theadditional thermoplastic resin is an acrylic resin.
 3. The aromaticpolycarbonate resin composition as claimed in claim 1 or 2, whichcontains from 0.005 to 0.2 parts by mass of a phosphorus-basedantioxidant relative to 100 parts by mass of the aromatic polycarbonateresin.
 4. The aromatic polycarbonate resin composition as claimed inclaim 3, wherein the phosphorus-based antioxidant is a pentaerythritolcompound.
 5. The aromatic polycarbonate resin composition as claimed inclaim 4, wherein the phosphorus-based antioxidant isbis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol phosphite.
 6. Thearomatic polycarbonate resin composition as claimed in any of claims 1to 5, which contains from 0.01 to 2 parts by mass of a functionalgroup-containing silicone compound and/or an alicyclic epoxy compoundrelative to 100 parts by mass of the aromatic polycarbonate resin.
 7. Atransparent molding of the aromatic polycarbonate resin composition ofany of claims 1 to
 6. 8. An optical waveguide made of the aromaticpolycarbonate resin composition of any of claims 1 to 6.